Chemical treatments are commonly applied to soil to deliver nutrients required by crops for optimal growth and production. For example, nitrogen-containing fertilizers such as ammonia and urea are commonly used by farmers to enhance corn crop yields. Soil can be treated during the growing or non-growing season, with most fertilizers typically being applied early in the growing season based on the consistency and moisture content and to avoid damage to growing crop.
The efficacy of chemical treatments can depend upon a number of factors. Such factors include, among others, the species and variety of crop being grown, the growth stage of the crop, the composition, moisture content, and pH of the soil, the presence of organic matter within the soil, weather conditions, hours of daylight, the nature of past and future chemical treatments, and the form and quantity of anticipated current chemical treatment.
For example, it is known that corn takes up, in the grain and stover, about one pound of nitrogen per bushel of grain produced. Only a small amount of this nitrogen is needed during the seedling stage of corn, while subsequent growth stages, such as the V8 growth stage, require significant higher quantities of nitrogen. Beginning with the V8 growth stage and continuing over a period of 30 days if conditions are favorable, corn can advance from approximately knee-high to the tassel stage of development. During this stage, corn may require over half its total nitrogen supply. Nitrogen deficiency at any time during a corn plant's life will impair yield. If the deficiency occurs during a rapid vegetative growth phase, however (such as at the beginning of the V8 growth stage), yield losses may be severe. It is therefore important to precisely determine the timing and amount of nitrogen applications. Accordingly, there is a need for a system that prescribes nitrogen or other nutrient and chemical applications based on the growth stage of a particular crop.
As another example, weather has a significant impact on the uptake of nutrients such as nitrogen by crops. In particular, temperature and moisture can impact the amount of nitrogen mineralized from the organic matter fraction of the soil. Excessive rainfall may cause nitrogen loss through leaching and saturation of the soil, causing the plant to run out of nitrogen prior to reaching rapid vegetative growth stages such as the V8 stage. Colder temperatures, such as those below 50 degrees Fahrenheit, generally cause soil microbial activity to be significantly slowed or stopped altogether. Excessively dry conditions may prevent nitrogen from moving from the point of application to the root zone of the plants.
Yet another important factor in the uptake of soil nutrients such as nitrogen is soil type. In particular, soil type plays an important role in determining soil moisture, including the water available to a plant. Differences in soil type can have a dramatic impact on the growth of a plant as well as its ability to recover from heat and moisture stress during different growth stages of its life cycle. Generally, sandy soils hold less water per foot of soil, subjecting plants to stress during dry periods. Clay soils hold more water than other soil textures, but plant roots are not able to extract the moisture needed from high-clay (small particle size) soils. Loamy soils provide the most usable amount of plant-available water per foot of soil. Soil type can therefore have a dramatic effect on the amount of residual nutrients remaining due to previous applications.
Additionally, the topography or terrain or slope (i.e., elevation change) across a field or within a zone or zones of a field can effect soil nutrient applications and so need to be considered along with previous and planned nitrogen applications.
The nature of past and future chemical treatments can also significantly affect the short-term and long-term projections for the nitrogen content soil. Common nitrogen fertilizers include anhydrous ammonia, urea-ammonium nitrate solutions, granular urea, ammonium nitrate and ammonium sulfate. Ammonium (NH4+) forms of nitrogen bind to negatively charged soil particles and are not subject to leaching or dentrification losses. This means that applying nitrogen fertilizers that include more ammonium and less nitrate forms of nitrogen reduces the potential for loss in the short term. However, over time, soil microbes convert the ammonium to nitrate (NO3−), which can be lost due to leaching or saturation during heavy or excessive rainfall. Urea-based fertilizers are also subject to loss through volatilization when surface applied. Volatilization potential is reduced when the urea is taken into the soil through rainfall, irrigation or tillage.
Accordingly, there is a need to model chemical application of crop nutrients based on current conditions and soil attributes that will allow farmers to reach desirable crop yield targets. There is a further need to develop prescriptions for such chemical applications in real time in conjunction with location-based soil sampling and analysis.
While location-based soil testing and analysis allows agricultural growers and providers to tailor seed variety and chemical applications to actual growing conditions, it has been difficult to obtain soil properties without the use of either large soil-collection machines or external laboratories. The use of external laboratories for soil testing is particularly problematic because soil samples must be sufficiently large to enable proper testing, must be removed and shipped from the site (thereby requiring appropriate labeling and tracking so that test results are accurately to the location of the sampling site). Additionally, soil testing at external laboratoriess is typically performed by drying out the soil sample, a process that can skew results.
An additional drawback to the use of external laboratories is the amount of time required to package, ship, and analyze a sample and report the corresponding results. Depending upon factors such as the locations of the sampling site and the laboratory, the day of the week on which shipment is made, and other externalities, such timeframes can range from several days to several weeks. During this time, changes may also occur to the soil sample and crops may be exposed to non-optimal soil conditions that can adversely affect desired crop yields. The detrimental effects of improper or unbalanced soil conditions can be particularly magnified during certain accelerated growth stages, such as the V8 stage for corn.
Automated soil collection devices have been developed that analyze soil on-location. Such automated soil analyzing machines are typically large attachments that must be pulled by the grower through the field of interest. Not only are such machines extremely expensive, but significant time is required to set up and attach the device to a tractor or other vehicle. Moreover, such devices generally cannot be used when crops are present due to the ensuing damage to the crops that would result during use. This restricts their operational usefulness to pre-planting or post-planting timeframes, effectively eliminating a farmer's ability to measure growing conditions during a plant's life cycle.
Furthermore, previous attempts to provide location-based soil analysis and sampling typically test the soil in a solid state. This may lead to potential damage to the analyzing sensors from rocks and other field debris. Others have attempted to address this issue. For example, U.S. Pat. No. 7,216,555 (“the '555 Patent”) attempts to address the potential for abrasion and damage to the sensors by providing pressure sensitive measurements—essentially allowing the sensors to move in response to rocks and other field debris. While this may help to minimize potential damage to the sensors, the additional shock absorbing sensor mounts add expense, weight and complexity to the device. Moreover, because the device measures the soil in solid form and because rocks and field debris can vary the position of the sensors, the test results may not accurately reflect the true composition of the soil that is sampled. Therefore, there is a need for a soil-testing apparatus and method which avoids the expense, complexity, and potential inaccuracies that may occur with the apparatus disclosed in the '555 Patent.
Others have attempted to provide robotic vehicles with built-in soil-testing laboratories. For example, U.S. Publication Number 2003/0112152 (“the '152 Publication) discloses a robotic vehicle and method for soil testing. This system is a dedicated autonomous system. While such systems can determine soil properties by location autonomously, they are not easily transportable and they are expensive. Moreover, a user of such systems cannot easily perform random tests of soil properties or replicate identical tests upon the occurrence of unexpected results. Additionally, farmers may want to ascertain the soil condition of a particular area of interest while they are physically present in the field. If the farmer were using the autonomous system of the '152 Publication, for example, the farmer would have to call out the robot, direct it to the specific location, wait for the robot to arrive, perform testing and upload results so that the farmer could understand the soil conditions at the farmer's present location. Therefore, it would be desirable to provide farmers with the ability to test soil conditions while in the field without the need to call up a dedicated soil testing autonomous system.
It would also desirable to have a soil testing apparatus that is compact enough for easy transport to and within a field, one that tolerates dust and temperature fluctuations, one that can absorb shock loads and vibrations and one that allows for the sensor to be operated in the field at any time.
A further drawback of soil-analyzing systems is that they fail to provide actionable information and instead only provide a farmer with information concerning the current properties of a soil sample. Requiring the farmer or an agronomist to correlate the soil properties from the soil analysis using various charts or algorithms to produce usable output from which a crop nutrient prescription can be derived—such as a recommended nitrogen application—which a farmer can then apply. This can result in additional delays, added complexity, increased cost and greater risk of error.
Thus, there is a need in the art for an apparatus, system and method for soil testing that is portable, easy to use, prevents damage to sensors and allows for on-site or location-based testing. There is a further need in the art for a soil testing method and apparatus that can prescribe an optimal chemical application (such as anhydrous or urea ammonium nitrate (UAN)) based on certain measured parameters (such as a nitrate reading in pounds per square inch), user input of various agronomic factors (such as yield target, crop growth rate at the time of sampling, and sample depth) and constants and conversion factors via a user interface integrated or connectable to a soil testing device.
In particular, there is a need in the industry to enable farmers to generate nitrogen balance and nitrogen needs-prediction for an area of interest beginning at the time of sampling and continuing for the remainder of a growing season to allow a farmer to take appropriate action to address soil condition in near real time during the growing season. There is a further need for a soil-testing apparatus and method which can generate soil-sampling prescriptions for a field or an area of interest within the field. There is also a need for a soil-testing apparatus and method for receiving and displaying a soil-sampling prescription, including pathing to soil sampling locations within the soil sample-prescription for a field or an area of interest within the field.